A Journey of Sans-discovery---Part 1: UnderFell
by Do Whatever You Want I'm Dead
Summary: Ever since Frisk finished the True Pacifist route and destroyed her ability to reset, Sans hasn't quite felt like himself. He takes a walk in Snowden Forest - and finds a different world! Now he has to get home - before he forgets who he truly is. Multi-AU series. Various ships. Each part will vary in rating, depending on the AU. Part 1: UnderFell
1. Chapter 1

**Okay, so this is Part 1 of a series that I am writing for Undertale. Each part will focus on a different AU, but every AU that appears before each part will be able to visit the new AU that is introduced in each part. I will not do every AU - there's over 700! No way in Hell I'm doing any of that shit!**

 **So, I'll focus on maybe 10 or so, maybe 20 if I keep up my interest in the series. Each part may or may not be small, but I'm planning on a wider story arc throughout the series, unlike the My Little Avengers crossover series I have written a few years ago.**

 **Each part may vary in rating, depending on the AU. There will be at least one that will be rated M for sexual content (I'm sure you guys can understand which AU I _really_ look forward to **┬┴┬┴┤ ͜ʖ ͡°) ├┬┴┬┴).

 **Please enjoy!**

* * *

Sans sighed and looked up at the sunset before him. Papyrus was right; it was beautiful. His seemingly perpetual smile widened slightly for his bro, knowing that Papyrus would be so happy for what time they had before the reset.

On cue, he walked back to the Underground to tell everyone. It didn't take long, and monsters were soon rushing to the surface to behold the sun, which no one had seen for so long. Well, to their memory. Sans…

He still remembered everything. Every reset, every monster's death. Surprisingly, Frisk had not gone genocidal. He was expecting it after all of this time, yet… they never did.

Sans sighed and finally let his smile fall into the first frown he'd had in a long time, even past resets. He couldn't let anyone know about how he truly felt; the only one who knew anything was Toriel, and she had known that small bit since before the resets began. How long ago was that?

 _Eh, doesn't matter,_ he thought as he got to Snowden Town, to the house he and Papyrus had moved into so long ago, after the accident…

He shook his head, chasing the thoughts away as he teleported to his monstrosity of a messy room. He just needed to go to sleep and wait till the reset happened. It wasn't even a minute after his head hit the pillow that he fell asleep, murmuring, "papyrus, you want anything?"

When his eyes next opened, he was surprised to see that he was not in his room, but rather in a strange room with two doors. One had a sign over it that said, True Reset, and the other's said, Continue. Frisk and Flowey were both in the room, and Flowey was talking to Frisk.

"Promise that I'll forget everything? That I'll be like… I never met you before?" the flower was asking, looking sad.

Looks like the flower knew about the resets, too. Figures.

Frisk said nothing, and Flowey sighed, saying, "I understand. It's more kindness than I deserve. Just go. I'll be fine."

Frisk held the True Knife in front of them, regarding it with deep thought. Sans drew in a breath. Maybe this would be the time the kid would finally go genocidal? Had Fate brought him here to witness that reset?

Suddenly, Sans was pulled out of his thoughts as the kid raised the True Knife in the air. _wait, what? would the kid kill the weed before resetting? that would certainly be a good start to a genocide run_ , he thought before the kid did something surprising: they destroyed the True Reset door, surprising both him and the weed.

"Y-you destroyed it," Flowey said in shock, solidifying the situation for them all.

The human nodded with a smile. They then said, "Everyone else is happy. Time to keep that happiness forever, right?"

Sans was genuinely surprised. What about the timeline where everything ends? Did they just… eradicate that possibility? He closed his eyes and looked at the timelines again. It was true; there was no reset anywhere in the future.

Frisk seemed to see Sans and smiled before turning to the Continue door and waving back to Flowey and saying, "Bye, Asriel!" before running outside into the sunlight.

Flowey looked after the kid before smiling and saying, "Bye, Frisk." He then went into the ground, probably to go somewhere else.

Sans stared at the ruined True Reset door for five minutes before leaving through the Continue door. It felt… strange, to be honest. Knowing that he did not have to witness the end of all things, knowing that even the possibility of resets was gone?

He had no idea what to do with himself now.

When he left the strange room, Frisk was waiting for him.

"so… no more resets?" he asked, putting back on his signature smile.

"Yup. No more resets," they replied, smiling in turn.

"heh… guess i was wrong, kiddo; looks like we keep this ending."

"You were so sure you wouldn't?" Frisk looked confused, as if this was their plan the whole time.

"well, yeah," he replied, shrugging. "it's never been otherwise before."

"Looks like you were wrong," they said smugly. "Well, whatcha gonna do now? We got no more resets; whatcha gonna do?"

Sans only shrugged. "dunno. i honestly don't think that i ever considered this at all."

Frisk nodded. "Well, I'm gonna go back to Mom. She's got breakfast ready by now. Wanna come with?"

Sans' eyes widened for a moment, then closed as he sighed and shrugged. "sure, kid. i've never got to try tori's cooking in any timeline."

He followed her back to Toriel's house for a hearty breakfast with a heavy heart and mind. What was he meant to do now?

Weeks passed, but Sans still felt out-of-place. Everyone else was settling in well: Toriel was teaching at Frisk's school and had adopted the kid, Undyne and Alphys were in a relationship and settling in with their careers, Asgore was gardening for the city, and Papyrus was… Papyrus. Mettaton had even begun an acting career with the humans.

And Sans? Well, right now he was back in Snowdin Forest, trying to figure out what to do now that there was no reset to worry about.

He walked through, failing to notice the trees changing around him.

* * *

 **A/N: Hey guys! Yep, I've gotten sucked into the Undertale fandom. It's a good day to be burning in a new section of Hell.**

 **Welp, I won't keep you guys long. Just so you all know, I'm back on FF, but I just got a new profile on AO3!**

 **Do_Whatever_You_Want_Im_Super_Dead**

 **Check it out!**

 **As this is my first Undertale fanfiction, please leave a review and tell me what you think!**


	2. Chapter 2

**A/N:**

 **Welp, didn't realize I'd take so long with this update... school has just started back up again and my time's been sucked away. That and I've found some amazing Undertale fanfictions and am currently fighting Sans in the game. It's not the best way to fight... but oh well! Comments are always welcome!**

 **In any case, I've decided on some AUs I will do for this series and an order!**  
 **1\. UnderFell (obviously)**  
 **2\. InkTale/ErrorTale**  
 **3\. UnderSwap**  
 **4\. MusicalTale**  
 **5\. UnderLust**  
 **6\. GenderSwap**  
 **7\. FlowerTale**  
 **8\. StoryShift**  
 **9\. AfterTale**

 **I'm thinking maybe adding in DreamTale or something, but Imma do research on everything before I do anything else. After all, I wanna figure out how everyone's gonna interact and all that shit.**

 **In any case, enjoy!**

* * *

Sans' first clue that he was no longer at home was a sudden flying red bone right past his skull. His eyes snapped up and his left eye glowed blue and yellow as he looked to the source of the attack: a skeleton who -

Sans' eyes went black in shock and fear. In front of him was... him. Albeit, this other him looked a bit different. Instead of a blue hoodie, this him wore a black coat with a fur lining. Instead of a white t-shirt, he wore a red turtleneck sweater. He still wore black basketball shorts, but he actually wore tennis shoes instead of pink slippers.

an alternate me? how's that possible? Sans thought.

"yo, who're you, asshole?" the other Sans asked, breaking Sans out of his thoughts and readying another bone attack, sharp red bones poised to strike.

"sans. sans the skeleton," Sans replied, readying a bone attack of his own, his normal white bones ready to strike at a moment's notice.

"that's impossible, since i'm sans," the other him scoffed.

"looks like an impossible day for both of us," Sans remarked, both of the skeletons' eyesockets black as they stood, ready to attack the other in a game of Chicken. Eventually, after a couple hours, they let the bones dissipate, clear to both of them that neither wanted to truly harm the other.

"so... sans, isn't it?" the other him asked, shoving his hands into his coat pockets.

"yeah. what's going on? one minute, i'm walking through snowdin forest, the next i'm fighting another me," Sans replied, shrugging and also shoving his mitten-covered hands in his pockets and looking at his doppelganger.

"welp, guess i'd better take you to my place. trust me, this place is probably a lot more dangerous than where you came from, if the way you're dressed has anything to say about it," the other him offered, turning around and ready to walk off.

Sans quickly started following the slightly larger skeleton (he hadn't noticed the height difference in the fight, but now that they were closer, he finally noticed), keeping an eyesocket out for anything that could possibly be a threat on his life. No one came out to try to kill him, but Sans kept himself ready for a potential battle, and the two Sanses soon reached Snowdin Town. Everything seemed to be mostly the same except that no one was friendly to anyone - most especially this darker version of himself. The two skeletons soon reached the other Sans' house, and they both quickly went inside before putting the door between themselves and the other monsters.

"well, at least no one tried to kill you, and my brother is out on patrol," the other Sans remarked. "just make yourself at home. there's spaghetti in the fridge if you're hungry, and my room is open to ya... not that there's much in there due to my bro being a total asshole."

"thanks," Sans replied, plopping down on the couch and sighing in slight relief. "to be honest, i thought that i'd be dusted any moment out there."

"trust me, in this world, it's KILL or BE KILLED, so i'd suggest getting some LOVE before you are killed. especially since you don't have any."

"heh, figures. i'm just gonna try to avoid anyone until i figure out how to get back home," Sans said with a shrug, "because this place is clearly not home."

Suddenly, the door slammed open, and a tall skeleton in black armor, a red scarf, the same pointed teeth as the other Sans, and resembled Papyrus barged into the house.

"SANS! WHY AREN'T YOU AT YOUR STATION?!" the skeleton yelled at the other Sans before suddenly noticing Sans on the couch. "AND WHO THE HELL DID YOU BRING INTO OUR HOUSE?!"

"sup?" Sans greeted. "i'm a different sans. don't ask me why i'm in this place instead of my own house, cause i don't know."

The other Sans groaned and facepalmed. "so much for avoiding everyone, huh?" he commented to Sans, to which Sans only gave a shrug.

"eh, i probably don't have the guts to do it anyways," Sans joked before chuckling at his own pun, which caused the other Sans to chuckle, too. Predictably, the taller skeleton groaned aloud.

"YOU'RE SANS, ALL RIGHT," the skeleton said, letting a long hand slide down his face. "I'M THE GREAT AND TERRIBLE PAPYRUS!" he introduced himself, placing a hand on his chest much like Sans' Papyrus would when talking about himself. "UGH, IT'S GOING TO BE CONFUSING TO HAVE TWO SANSES HERE."

Sans was still slightly reeling over the fact that there was a world with a different Sans and Papyrus, and missed the last comment.

"how about calling me 'red', boss?" the other Sans suggested. "he can be blue because of his hoodie."

"SO YOU DO HAVE AN INTELLIGENT BRAIN IN THAT WORTHLESS HEAD OF YOURS," Papyrus said, smiling as he noogied the other Sans - er, Red. "WELL, SINCE BLUE IS CLEARLY NEW HERE, IT WOULD BE BEST IF HE STAYS WITH US. AFTER ALL, EVERY MONSTER IN THE UNDERGROUND WILL WANT TO KILL HIM."

"wait, what? are you serious right now?" Sans asked, extremely concerned.

Papyrus sighed, facepalming again. "I THINK YOUR OTHER SELF WOULD BETTER TELL YOU THAN I. I'M GOING TO MAKE DINNER. PLEASE TRY NOT TO DESTROY THE LIVING ROOM."

Papyrus left the room, leaving the two short skeletons on their own with their much-needed-to-answer question hanging over them.


End file.
